Faulty internal temperature sensor inside the transmission fluid pump control module; Damaged or corroded wiring harness or connector at the control module; Open or short circuit in the sensor wiring between the module and the sensor; Failed control module due to internal electronics failure; Poor ground connection for the control module; Software glitch or corrupted calibration in the control module

DTC codes / P0Cxx · Hybrid propulsion / P0C1C

P0C1CElectric/Auxiliary Transmission Fluid Pump Control Module Internal Temperature Sensor Circuit

P0C1C indicates that the electric or auxiliary transmission fluid pump control module has detected an internal fault in its temperature sensor circuit. The control module monitors its own internal temperature to protect the pump and transmission, and when the sensor signal falls outside the expected range, it stores this code and may disable the auxiliary pump.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

AreaHybrid propulsion

Symptoms you may notice

Illumination of the check engine light or service transmission warning
Transmission may enter limp mode or fail to engage drive or reverse
Overheating of the transmission during low-speed or stop-and-go driving
Reduced fuel economy due to improper pump operation
Often no symptoms besides the warning light

Common causes, most likely first

Faulty internal temperature sensor inside the transmission fluid pump control module
Damaged or corroded wiring harness or connector at the control module
Open or short circuit in the sensor wiring between the module and the sensor
Failed control module due to internal electronics failure
Poor ground connection for the control module
Software glitch or corrupted calibration in the control module

How to diagnose and fix it

Use a scan tool to verify the code and check for any related pending or history codes
Inspect the control module connector and wiring for damage, corrosion, or loose pins
Measure resistance and voltage on the temperature sensor circuit to check for opens or shorts
Check the control module ground circuit for excessive resistance
If wiring and connections are good, replace the transmission fluid pump control module
After replacement, clear codes and perform a relearn or calibration procedure if required
Road test the vehicle to confirm the code does not return and the auxiliary pump operates correctly

Don't overlook the pump control module ground

A poor ground connection at the control module can cause the internal temperature sensor to read incorrectly, mimicking a failed sensor.
The code may set intermittently due to vibration or heat, so always wiggle-test the harness while monitoring live data.
Some vehicles use the auxiliary pump only during auto start-stop events, so the driver may never notice a performance issue.
Replacing the control module without checking the sensor circuit can lead to repeat failure if the root cause is damaged wiring.
This code is often misdiagnosed as a transmission fluid overheating issue when the actual problem is electrical.

Can I keep driving with P0C1C?

It is generally safe to drive with this code if the transmission is not overheating and the vehicle is not in limp mode, but avoid heavy towing or prolonged low-speed driving that relies on the auxiliary pump. If the transmission overheats or shifts harshly, stop driving and seek service immediately.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.